Voltage regulator feedback protection method and apparatus

ABSTRACT

An integrated circuit includes an output terminal. A plurality of feedback terminals receives a feedback signal. A voltage regulator has a feedback input in communication with the plurality of feedback terminals to receive the feedback signal. The voltage regulator has a power output in communication with the output terminal. The voltage regulator is responsive to the feedback signal to generate the power output.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional of U.S. patent application Ser. No.10/846,717 filed May 13, 2004. The disclosure of the above applicationis incorporated herein by reference in its entirety.

TECHNICAL FIELD

An aspect of this invention relates to power systems for electroniccircuits.

BACKGROUND

Most modern electronic systems are powered by one or more voltageregulators that provide regulated output power to the system. A typicalvoltage regulator includes a feedback signal extending from the powerinput to the system back to the DC/DC converter. The feedback signal isused in the voltage regulator to regulate the output power at the inputto the system, thereby reducing error in the regulated output that mightbe caused by conduction losses between the voltage regulator and thesystem.

FIG. 1 shows a typical conventional feedback system used with a voltageregulator 12 and electronic system 14. An integrated circuit 16 mayinclude the voltage regulator 12 and connect via a pin 17 to externalfilter components such as an output inductor 18 and output capacitor 20.A feedback signal 22 from the regulated output, Vout, may connect to thevoltage regulator via a pin 19. The feedback signal 22 is typicallyreceived from a junction of the output inductor 18 and the outputcapacitor 20 so that gain and phase associated with the filtercomponents is included within the control loop of the voltage regulator12. The feedback signal may additionally be obtained from a point nearerto the input to the electronic system 14 to minimize the error caused byparasitic effects such as conduction losses and leakage inductance.

Although, sensing the junction of the filter components to generate thefeedback signal may improve the stability and accuracy of the regulatedoutput of the voltage regulator 12, if the line carrying the feedbacksignal becomes electrically degraded, the regulated output may driftoutside of the regulation limits causing the voltage regulator 12 toshutdown.

SUMMARY

An integrated circuit comprising a feedback terminal to receive afeedback signal. A voltage regulator has a feedback input to receive thefeedback signal from the feedback terminal. The voltage regulator has apower output in communication with an output terminal. The voltageregulator being responsive to the feedback signal, to generate the poweroutput. A voltage generator to generate a pull-up voltage having anamplitude greater than a DC voltage amplitude of the power output. Thepull-up voltage being derived separately from the power output. Apull-up resistor in communication with the pull-up generator and thefeedback input of the voltage regulator.

The details of one or more embodiments of the invention are set forth inthe accompanying drawings and the description below. Other features,objects, and advantages of the invention will be apparent from thedescription and drawings, and from the claims.

DESCRIPTION OF DRAWINGS

FIG. 1 is a block diagram of an aspect of a conventional power supplyfeedback system.

FIG. 2 is a block diagram of a power distribution system that includesan aspect of a feedback protection system.

FIG. 3 is a block diagram of a power distribution system that includesanother aspect of a feedback protection system.

FIG. 4 is a block diagram of a power distribution system that includesanother aspect of a feedback protection system.

Like reference symbols in the various drawings indicate like elements.

DETAILED DESCRIPTION

FIG. 2 shows a block diagram of an aspect of a power distribution system30 for supplying a regulated output voltage, Vout, to a system 35 suchas an electronic system. The power distribution system 30 includes afeedback protection system 50 to protect the power distribution system30 from the potential effects of a feedback line 32 that is electricallydegraded from normal operation, wherein electrically degraded is definedas having an increased impedance that causes a feedback signal on thefeedback line 32 to be of insufficient quality for the control loop ofthe power distribution system 30 to control the regulated outputvoltage. The increased impedance of the feedback line 32 may be due toany cause such as a cold solder joint, the feedback line 32 beingpartially disconnected from the regulated output voltage, and thefeedback line 32 being completely disconnected from the regulated outputvoltage.

A voltage regulator 34 may generate the regulated output voltage, Vout,from an input voltage, Vin, and supply that regulated output voltage tothe system 35. The voltage regulator 34 may be any type of voltageregulator such as switching regulators and linear regulators. Anintegrated circuit 36 may include the voltage regulator 34 and connectvia one or more output terminals 38 to external filter components suchas an output inductor 40 and output capacitor 42. Any type of terminalsmay be used for the output terminals 38 such as pins, ball grid arrays,and connectors. The voltage regulator 34 may generate a power output,Vc, that is filtered by the external filter components to generate Vout.The power output, Vc, may be any type of power output to be used forpowering the system 35 such as a chopped output of a switching regulatorthat is filtered by the external filter components, and a DC output fromeither a switching regulator or a linear regulator.

The feedback line 32 may connect from the regulated output, Vout, to thevoltage regulator via one or more feedback terminals 44. Any type ofterminals may be used for the feedback terminals 44 such as pins, ballgrid arrays, and connectors. A feedback signal carried on the feedbackline 32 may be sensed at a junction of the output inductor 40 and theoutput capacitor 42 such as near an input 37 to the system 35.

The integrated circuit 36 may include a feedback protection system toprotect the system 35 if the feedback line 32 is electrically degraded.In another aspect, the feedback protection system 50 may monitor thefeedback line 32 and detect if feedback line 32 is electricallydegraded. The feedback protection system 50 may include a pull-upresistor 46 connected between the feedback line 32 and a pull-upvoltage. The pull-up resistor 46 may apply the pull-up voltage throughthe relatively high impedance of the pull-up resistor 46 to the feedbackline 32. The pull-up resistor 46 advantageously causes the outputvoltage to decrease if the feedback line 32 is electrically degraded.

In one aspect, when the feedback line 32 is electrically degraded, avoltage that is greater than Vout is applied through the pull-upresistor 46 to the voltage regulator 34 causing the control loop of thevoltage regulator 32 to reduce the conduction time of the converter 32leading to a decrease in the output voltage. Conventional DC/DCconverters that have a disconnected feedback line is electricallydegraded, typically generate a greater output voltage that may cause anovervoltage circuit to trigger, leading to shutdown of the converter.The feedback protection circuit 50 may advantageously operate if thefeedback line 32 is electrically degraded to cause the control loop ofthe voltage regulator 32 to decrease the output voltage instead ofrelying on a overvoltage protection circuit. In addition, the feedbackprotection circuit 50 may cause the output voltage to decrease withoutfirst increasing.

In another aspect, if the feedback line 32 is electrically degraded fromthe integrated circuit 36 the pull-up voltage that is applied throughthe pull-up resistor 46 is high enough to cause the overvoltage circuitin the voltage regulator 34 to trigger an overvoltage shutdown of thevoltage regulator 34 causing the output voltage to decrease toapproximately zero volts. Although the overvoltage circuit operates toshutdown the voltage regulator 34 if the feedback line 32 iselectrically degraded, the output voltage does not initially increase,but instead initially decreases. Although the shutdown circuiteventually causes the voltage regulator 34 to shutdown, the initialdecrease in the output voltage may be due to operation of either thecontrol loop or the overprotection circuit depending on their relativespeed of operation.

The pull-up resistor 46 may be any suitable resistance to pull-up thefeedback line 32 to approximately the pull-up voltage if the feedbackline 32 is electrically degraded. Exemplary values of the resistance mayrange from approximately 100 ohms to 1 Meg ohms, although the resistancemay be greater than or less than this range depending on several designfactors such as the differential between the pull-up voltage and theoutput voltage, and the impedance of interface circuits that connect tothe pull-up resistor 46. Although only a single pull-up resistor 46 isshown, another pull-up resistor may be coupled to a feedback return lineif differential feedback sensing is employed.

A voltage generator 54 may generate the pull-up voltage that is appliedto the pull-up resistor 46. The pull-up voltage may be any voltage thatis greater than Vout such as a voltage that is approximately 20% greaterthan Vout. Any energy source may be used for generating the pull-upvoltage such as the input voltage, Vin, and voltages from the voltageregulator 34.

A feedback monitor 56 may monitor the feedback line 32 within theintegrated circuit 50 to detect if the portion of the feedback line 32extending from the regulated output voltage through the feedbackterminal 44 is electrically degraded. The feedback monitor 56 maycommunicate a feedback degraded signal to the voltage regulator 34 toindicate that the feedback line 32 has an increased impedance. In oneaspect, the feedback monitor 56 may compare the voltage on a portion ofthe feedback line 32 internal to the integrated circuit 36 to areference voltage to determine if the feedback line 32 is electricallydegraded.

FIG. 3 shows an aspect of a power distribution system 100 for supplyinga regulated output voltage, Vout, to a system 102 such as an electronicsystem. The power distribution system 100 includes a feedback protectionsystem 104 to protect the power distribution system 100 from thepotential effects of a feedback line 106 that is electrically degradedfrom normal operation, wherein electrically degraded is defined ashaving an increased impedance that causes a feedback signal on thefeedback line 106 to be of insufficient quality for the control loop ofthe power distribution system 100 to control the regulated outputvoltage. The increased impedance of the feedback line 106 may be due toany cause such as a cold solder joint, the feedback line 106 beingpartially disconnected from the regulated output voltage, and thefeedback line 106 being completely disconnected from the regulatedoutput voltage.

A voltage regulator 108 may generate the regulated output voltage, Vout,from an input voltage, Vin, and supply that regulated output voltage tothe system 102. The voltage regulator 108 may be any type of voltageregulator such as switching regulators and linear regulators. Anintegrated circuit 110 may include the voltage regulator 108 and connectvia one or more output terminals 112 to external filter components suchas an output inductor 114 and output capacitor 116. The voltageregulator 108 may generate a power output, Vc, that is filtered by theexternal filter components to generate Vout. The power output, Vc, maybe any type of power output to be used for powering the system 35 suchas a chopped output of a switching regulator that is filtered by theexternal filter components, and a DC output from either a switchingregulator or a linear regulator.

Multiple feedback lines 106 may connect from the regulated output, Vout,to the voltage regulator via two or more feedback terminals 118. Afeedback signal carried on the feedback lines 106 may be sensed at ajunction of the output inductor 114 and the output capacitor 116 such asnear an input 120 to the system 102. The feedback protection system 104may comprise the feedback terminals 118 and interconnection of thefeedback terminals 118 within the integrated circuit 110. The feedbackprotection system 104 advantageously provides redundant feedback lines106 and feedback terminals 118 to prevent the electrical degradation ofany one of the feedback lines from affecting the operation of thevoltage regulator 108. For example, if there is a cold solder joint atone of the feedback terminals 118 causing the impedance of theassociated feedback line 106 to increase, the other feedback line(s) 106and feedback pin(s) 106 provide a redundant low impedance path for thefeedback signal.

FIG. 4 shows an aspect of another power distribution system 230 forsupplying a regulated output voltage, Vout, to a system 235 such as anelectronic system. The power distribution system 230 is similar to powerdistribution system 30 in function with corresponding elements numberedin the range 230-260, except that the power distribution system 230includes a signal generator 254 instead of the voltage generator 54 andthe pull-up resistor 46.

The signal generator 254 may be any type of high impedance signalgenerator such as a current generator, and a voltage generator with aseries resistor. The output impedance of the signal generator may beselected to be sufficiently high to not load down the source of thefeedback signal. For example, if the feedback signal is derived from aninductor-capacitor filter such as inductor 240 and capacitor 242 thesource impedance of the inductor-capacitor filter is very low, beingapproximately 0 ohms, therefore the output impedance may be anyimpedance greater than approximately 10 ohms.

The signal generator 254 may be any type of source including analternating current (AC) source and a direct current (DC) source. In oneaspect, when the signal generator 254 is an AC source, a tone detectormay monitor the feedback input of the voltage regulator 234 to detect anAC signal from the AC source, which indicates a degraded electricalcondition of the feedback line 232 and feedback terminal 244. In oneaspect, the feedback monitor 256 may comprise the tone detector.

A number of embodiments of the invention have been described.Nevertheless, it will be understood that various modifications may bemade without departing from the spirit and scope of the invention.Accordingly, other embodiments are within the scope of the followingclaims.

1. An integrated circuit comprising; an output terminal; a plurality offeedback terminals to each receive a feedback signal; and a voltageregulator that has a feedback input in communication with the pluralityof two feedback terminals to receive the feedback signal and that has apower output in communication with the output terminal, wherein thevoltage regulator generates the power output in response to the feedbacksignal.
 2. A power distribution system comprising: the integratedcircuit of claim 1; and external filter components that are coupled theoutput terminal and that comprise: an output inductor; and an outputcapacitor to filter the power output to generate a regulated outputvoltage.
 3. The integrated circuit of claim 1 wherein the voltageregulator is selected from a group consisting of a switching regulatorand a linear regulator, wherein the output terminal is selected from agroup consisting of a pin, a ball grid array, and a connector, andwherein the plurality of feedback terminals are selected from a groupconsisting of pins, ball grid arrays, and connector.
 4. The integratedcircuit of claim 1 further comprising an interconnection circuit tointerconnect each of the plurality of two feedback terminals to thefeedback input of the voltage regulator.
 5. The integrated circuit ofclaim 1 further comprising: a filter to generate a regulated outputvoltage from the power output, wherein the feedback signal is derivedfrom the regulated output voltage.
 6. A power distribution systemcomprising: the integrated circuit of claim 1; a filter to generate aregulated output voltage in response to the power output; and redundantfeedback lines coupled between the regulated output voltage and theplurality of feedback terminals of the integrated circuit to conduct thefeedback signal.
 7. The integrated circuit of claim 1 furthercomprising: a voltage generator to generate a pull-up voltage having anamplitude greater than a DC voltage amplitude of the power output,wherein the pull-up voltage is derived separately from the power output;and a pull-up resistor in communication between the pull-up voltage andthe feedback input of the voltage regulator.
 8. The integrated circuitof claim 7 wherein the pull-up voltage is approximately 120% of the DCvoltage amplitude of the power output, wherein the pull-up resistor hasan impedance in a range of approximately 100 ohms to 1,000,000 ohms, andwherein the voltage generator is a source type selected from a groupconsisting of an AC source and a DC source.
 9. An integrated circuitcomprising; an output terminal; a feedback terminal to receive afeedback signal; a voltage regulator that includes a feedback input toreceive the feedback signal from the feedback terminal and a poweroutput in communication with the output terminal, wherein the voltageregulator generates the power output and is responsive to the feedbacksignal; and a signal generator having an output impedance at least tentimes greater than an output impedance of the feedback terminal, whereinthe signal generator generates a pull-up signal in communication withthe feedback input.
 10. The integrated circuit of claim 9 wherein thesignal generator is selected from a group consisting of a currentsource, and a voltage source with an output resistor.
 11. The integratedcircuit of claim 9 further comprising: a filter to generate a regulatedoutput voltage from the power output, wherein the feedback signal isderived from the regulated output voltage.
 12. A power distributionsystem comprising: the integrated circuit of claim 11; and a feedbackline to conduct the feedback signal from the regulated output voltage tothe feedback terminal.
 13. A power distribution system comprising: theintegrated circuit of claim 9; external filter components that arecoupled to the output terminal and that comprise an output inductor andan output capacitor to filter the power output to generate a regulatedoutput voltage, wherein the feedback signal is derived from theregulated output voltage.
 14. The integrated circuit of claim 9 whereinthe voltage regulator is selected from a group consisting of a switchingregulator and a linear regulator, wherein the output terminal isselected from a group consisting of a pin, a ball grid array, and aconnector, and wherein the feedback terminal is selected from a groupconsisting of a pin, a ball grid array, and a connector.
 15. Theintegrated circuit of claim 12 further comprising a feedback monitor todetect an electrically degraded connection between the feedback terminaland the regulated output voltage.
 16. The integrated circuit of claim 15wherein the power output has an amplitude; and wherein the electricallydegraded connection is defined as having an increased impedance thatcauses the feedback signal to be of insufficient quality for the voltageregulator to control the amplitude of the power output.
 17. Theintegrated circuit of claim 15 wherein the electrically degradedconnection is selected from a group consisting of a cold solder joint,the feedback line being partially disconnected from the regulated outputvoltage, and the feedback line being completely disconnected from theregulated output voltage.
 18. The integrated circuit of claim 15 whereinthe feedback monitor compares a voltage of the feedback terminal to areference voltage to detect the electrically degraded connection. 19.The integrated circuit of claim 9 further comprising at a plurality offeedback terminals to each receive the feedback signal.
 20. A powerdistribution system comprising: the integrated circuit of claim 19; afilter to generate a regulated output voltage from the power output; andredundant feedback lines coupled between the regulated output voltageand the plurality of feedback terminals of the integrated circuit toconduct the feedback signal.
 21. The integrated circuit of claim 19further comprising an interconnection circuit to interconnect theplurality of feedback terminals.